Frew Nelson M.

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Nelson M.

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  • Article
    Air-sea gas transfer : its dependence on wind stress, small-scale roughness, and surface films
    (American Geophysical Union, 2004-08-21) Frew, Nelson M. ; Bock, Erik J. ; Schimpf, Uwe ; Hara, Tetsu ; Haußecker, Horst ; Edson, James B. ; McGillis, Wade R. ; Nelson, Robert K. ; McKenna, Sean P. ; Uz, B. Mete ; Jahne, B.
    The influence of wind stress, small-scale waves, and surface films on air-sea gas exchange at low to moderate wind speeds (<10 m s−1) is examined. Coincident observations of wind stress, heat transfer velocity, surface wave slope, and surface film enrichments were made in coastal and offshore waters south of Cape Cod, New England, in July 1997 as part of the NSF-CoOP Coastal Air-Sea Chemical Fluxes study. Gas transfer velocities have been extrapolated from aqueous heat transfer velocities derived from infrared imagery and direct covariance and bulk heat flux estimates. Gas transfer velocity is found to follow a quadratic relationship with wind speed, which accounts for ~75–77% of the variance but which overpredicts transfer velocity in the presence of surface films. The dependence on wind stress as represented by the friction velocity is also nonlinear, reflecting a wave field-dependent transition between limiting transport regimes. In contrast, the dependence on mean square slope computed for the wave number range of 40–800 rad m−1 is found to be linear and in agreement with results from previous laboratory wind wave studies. The slope spectrum of the small-scale waves and the gas transfer velocity are attenuated in the presence of surface films. Observations over large-scale gradients of biological productivity and dissolved organic matter show that the reduction in slope and transfer velocity are more clearly correlated with surface film enrichments than with bulk organic matter concentrations. The mean square slope parameterization explains ~89–95% of the observed variance in the data and does not overpredict transfer velocities where films are present. While the specific relationships between gas transfer velocity and wind speed or mean square slope vary slightly with the choice of Schmidt number exponent used to scale the heat transfer velocities to gas transfer velocities, the correlation of heat or gas transfer velocity with mean square slope is consistently better than with wind speed.
  • Technical Report
    Gas chromatography-mass spectrometry facility : recent improvements and applications
    (Woods Hole Oceanographic Institution, 1980-03) Frew, Nelson M. ; Sawdo, Richard M.
    Marine organic and organic geochemical studies require the best available performance in trace analysis of organic compounds in environmental samples. This report briefly outlines some of the recent improvements in the experimental capabilities of the Chemistry Department Gas Chromatography/Mass Spectrometry Facility (GC/MS Facility) from a user-oriented and non-technical viewpoint. These improvements include principally the interfacing of high performance glass capillary columns with Finnigan 1015 and 3200 quadrupole mass spectrometers, and the adaptation of the latter for use with selective chemical ionization (CI) techniques. Some of the new capabilities available using combined glass capillary GC/EI-MS and CI-MS are illustrated with examples from research in several areas of marine organic chemistry. These include studies of volatile organics in seawater, the distributions of various lipid class compounds in marine phytoplankton, sediments and particulate matter, and the behavior of anthropogenic pollutants in natural and artificial marine ecosystems.
  • Preprint
    Air-sea gas transfer velocity estimates from the Jason-1 and TOPEX altimeters : prospects for a long-term global time series
    ( 2006-03-02) Glover, David M. ; Frew, Nelson M. ; McCue, Scott J.
    Estimation of global and regional air–sea fluxes of climatically important gases is a key goal of current climate research programs. Gas transfer velocities needed to compute these fluxes can be estimated by combining altimeter-derived mean square slope with an empirical relation between transfer velocity and mean square slope derived from field measurements of gas fluxes and small-scale wave spectra [Frew, N.M., Bock, E.J., Schimpf, U., Hara, T., Hauβecker, H., Edson, J.B., McGillis, W.R., Nelson, R.K., McKenna, S.P., Uz, B.M., Jähne, B., 2004. Air–sea gas transfer: Its dependence on wind stress, small-scale roughness and surface films, J. Geophys. Res., 109, C08S17, doi: 10.1029/2003JC002131.]. We previously reported initial results from a dual-frequency (Ku- and C-band) altimeter algorithm [Glover, D.M., Frew, N.M., McCue, S.J., Bock, E.J., 2002. A Multi-year Time Series of Global Gas Transfer Velocity from the TOPEX Dual Frequency, Normalized Radar Backscatter Algorithm, In: Gas Transfer at Water Surfaces, editors: Donelan, M., Drennan, W., Saltzman, E., and Wanninkhof, R., Geophysical Monograph 127, American Geophysical Union, Washington, DC, 325–331.] for estimating the air–sea gas transfer velocity (k) from the mean square slope of short wind waves (40–100 rad/m) and derived a 6-year time series of global transfer velocities based on TOPEX observations. Since the launch of the follow-on altimeter Jason-1 in December 2001 and commencement of the TOPEX/Jason-1 Tandem Mission, we have extended this time series to 12 years, with improvements to the model parameters used in our algorithm and using the latest corrected data releases. The prospect of deriving multi-year and interdecadal time series of gas transfer velocity from TOPEX, Jason-1 and follow-on altimeter missions depends on precise intercalibration of the normalized backscatter. During the Tandem Mission collinear phase, both satellites followed identical orbits with a mere 73-s time separation. The resulting collocated, near-coincident normalized radar backscatter (σ°) data from both altimeters present a unique opportunity to intercalibrate the two instruments, compare derived fields of transfer velocity and estimate the precision of the algorithm. Initial results suggest that the monthly gas transfer velocity fields generated from the two altimeters are very similar. Comparison of along-track Ku-band and C-band σ° during the collinear phase indicates that observed discrepancies are due primarily to small offsets between TOPEX and Jason-1 σ°. The Jason-1 k values have an apparent bias of + 4% relative to TOPEX, while the precision estimated from the two observation sets is 5–7% and scales with k. The resultant long-term, global, mean k is 16 cm/h.
  • Article
    Investigations of air-sea gas exchange in the CoOP Coastal Air-Sea Chemical Exchange project
    (Oceanography Society, 2008-12) Edson, James B. ; DeGrandpre, Michael D. ; Frew, Nelson M. ; McGillis, Wade R.
    The exchange of CO2 and other gases across the ocean-air interface is an extremely important component in global climate dynamics, photosynthesis and respiration, and the absorption of anthropogenically produced CO2. The many different mechanisms and properties that control the air-sea flux of CO2 can have large spatial and temporal variability, particularly in the coastal environment. The need for making short-time-scale and small-spatial-scale estimates of gas transfer velocity, along with the physical and chemical parameters that affect it, provided a framework for the field experiments of the Coastal Ocean Processes Program (CoOP) Coastal Air-Sea Chemical Exchange (CASCEX) program. As such, the CASCEX project provided an opportunity to develop some of the first in situ techniques to estimate gas fluxes using micrometeorological and thermal imagery techniques. The results reported from the CASCEX experiments represent the first step toward reconciling the indirect but widely accepted estimates of gas exchange with these more direct, higher-resolution estimates over the coastal ocean. These results and the advances in sensor technology initiated during the CASCEX project have opened up even larger regions of the global ocean to investigation of gas exchange and its role in climate change.
  • Technical Report
    Hydrocarbons, polychlorinated biphenyls, and DDE in mussels and oysters from the U.S. Coast - 1965-1978 - the mussel watch
    (Woods Hole Oceanographic Institution, 1982-10) Farrington, John W. ; Risebrough, Robert W. ; Parker, Patrick L. ; Davis, Alan C. ; De Lappe, Brock ; Winters, Kenneth ; Boatwright, Dan ; Frew, Nelson M.
    Mytilus edulis, Mytilus californianus, Crassostrea virginica and Ostrea equestris were sampled at 90 to 100 stations around the United States coastline during each of three years- 1976, 1977, 1978. Data for concentrations of PCB, DDE, total hydrocarbons, gas chromatographically unresolved complex mixture hydrocarbons, and selected aromatic hydrocarbons are presented for most of the samples. Similar data for monthly samples of Mytilus edulis from Narragansett Bay, Rhode Island, U.S.A. and Mytilus californianus from Bodega Head, California, U.S.A. and laboratory intercalibrations are presented and discussed. Monthly temporal changes of factors of two to ten were found for ·organic pollutants in mussels from the Narragansett Bay station. Concentrations of PCBs and fossil fuel hydrocarbons for some urban stations were one to two orders of magnitude higher than those in remote areas. The northeast "megapolis" of the U.S. coast from the Chesapeake Bay area to Boston, Massachusetts clearly shows elevated concentrations of PCBs and fossil fuel hydrocarbons. The composition of aromatic hydrocarbons in samples with elevated concentrations shows both the influence of oil spill or chronic oil inputs and pyrogenic sources.
  • Article
    Gradients in dimethylsulfide, dimethylsulfoniopropionate, dimethylsulfoxide, and bacteria near the sea surface
    (Inter-Research, 2005-06-23) Zemmelink, Hendrik J. ; Houghton, Leah A. ; Sievert, Stefan M. ; Frew, Nelson M. ; Dacey, John W. H.
    Gradients of dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP), dimethylsulfoxide (DMSO), and bacterial numbers and diversity from the surface microlayer to 500 cm depth were assessed in coastal waters surrounding the Martha’s Vineyard Coastal Observatory, Massachusetts, USA. Microlayer samples were collected with a surface skimmer: a partially submerged, rotating glass cylinder (‘drum’) that allows the collection of a thin layer of water by adherence to the drum. A depletion of DMS towards the water surface (10 cm) was found at all sampling days, with largest gradients during rough sea surface conditions. The steep gradients show that gas fluxes and transfer velocities, based on the concentration disequilibrium between the water and the atmosphere, need to be based on near surface gas concentration values. Elevated DMSP, DMSO concentrations and bacterial numbers were found at the sea surface during calm conditions. Although degassing and photo-oxidation on the skimmer will bias the microlayer data, the results indicate stratification of DMSP, DMSO and bacteria during periods of smooth sea surface conditions.
  • Article
    The coupled boundary layers and air-sea transfer experiment in low winds
    (American Meteorological Society, 2007-03) Edson, James B. ; Crawford, Timothy ; Crescenti, Jerry ; Farrar, J. Thomas ; Frew, Nelson M. ; Gerbi, Gregory P. ; Plueddemann, Albert J. ; Trowbridge, John H. ; Weller, Robert A. ; Williams, Albert J.
    The Office of Naval Research's Coupled Boundary Layers and Air–Sea Transfer (CBLAST) program is being conducted to investigate the processes that couple the marine boundary layers and govern the exchange of heat, mass, and momentum across the air–sea interface. CBLAST-LOW was designed to investigate these processes at the low-wind extreme where the processes are often driven or strongly modulated by buoyant forcing. The focus was on conditions ranging from negligible wind stress, where buoyant forcing dominates, up to wind speeds where wave breaking and Langmuir circulations play a significant role in the exchange processes. The field program provided observations from a suite of platforms deployed in the coastal ocean south of Martha's Vineyard. Highlights from the measurement campaigns include direct measurement of the momentum and heat fluxes on both sides of the air–sea interface using a specially constructed Air–Sea Interaction Tower (ASIT), and quantification of regional oceanic variability over scales of O (1–104 mm) using a mesoscale mooring array, aircraft-borne remote sensors, drifters, and ship surveys. To our knowledge, the former represents the first successful attempt to directly and simultaneously measure the heat and momentum exchange on both sides of the air–sea interface. The latter provided a 3D picture of the oceanic boundary layer during the month-long main experiment. These observations have been combined with numerical models and direct numerical and large-eddy simulations to investigate the processes that couple the atmosphere and ocean under these conditions. For example, the oceanic measurements have been used in the Regional Ocean Modeling System (ROMS) to investigate the 3D evolution of regional ocean thermal stratification. The ultimate goal of these investigations is to incorporate improved parameterizations of these processes in coupled models such as the Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS) to improve marine forecasts of wind, waves, and currents.
  • Technical Report
    No. 2 fuel oil compound retention and release by Mytilus edulis : 1983 Cape Cod Canal oil spill
    (Woods Hole Oceanographic Institution, 1986-03) Farrington, John W. ; Xiaoping, Jia ; Clifford, C. Hovey ; Tripp, Bruce W. ; Livramento, Joaquim B. ; Davis, Alan C. ; Frew, Nelson M. ; Johnson, Carl G.
    Retention and release of No. 2 fuel oil compounds by Mytilus edulis contaminated by a small oil spill in the Cape Cod Canal in 1983 has been studied for the population "in situ" and for a subsample transplanted to a clean laboratory seawater system. Compounds analyzed include C13 to C24 n-alkanes; pristane; phytane; C2-, C3-naphthalenes; fluorene; phenanthrene; C1-, C2-, C3-phenanthrenes; fluoranthene; pyrene and dibenzothiophene. Biological half-lives were determined for the compounds from Day-3 to Day-29 following the spill and ranged from 1.5 days for C2-naphthalenes to 9.9 days for C2-phenanthrenes. Biological half-lives for the unresolved complex mixture determined by gas chromatographic analyses were 17 days for the alkane-cycloalkane fraction and 35 days for the aromatic fraction. Results compared favorably with data from a small oil spill contaminating the same mussel population at the same time of the year in 1978, although marked differences were noted for certain parameters. Gas chromatographic-mass spectrometer analyses of C2- and C3-phenanthrenes revealed changes in relative abundance of compounds within isomer groups from samples at Day-29 to the time when no further detection of fuel oil was noted. These results suggest a release or metabolism of these compounds which is molecular structure specific. This study also demonstrated the feasibility of training an analyst unfamiliar with analyses of hydrocarbons in tissues to conduct high resolution glass capillary GC analyses and some aspects of GCMS data systems output within a period of four to five months.
  • Article
    A new approach to estimation of global air-sea gas transfer velocity fields using dual-frequency altimeter backscatter
    (American Geophysical Union, 2007-11-03) Frew, Nelson M. ; Glover, David M. ; Bock, Erik J. ; McCue, Scott J.
    A new approach to estimating air-sea gas transfer velocities based on normalized backscatter from the dual-frequency TOPEX and Jason-1 altimeters is described. The differential scattering of Ku-band (13.6 GHz) and C-band (5.3 GHz) microwave pulses is used to isolate the contribution of small-scale waves to mean square slope and gas transfer. Mean square slope is derived for the nominal wave number range 40–100 rad m−1 by differencing mean square slope estimates computed from the normalized backscatter in each band, using a simple geometric optics model. Model parameters for calculating the differenced mean square slope over this wave number range are optimized using in situ optical slope measurements. An empirical relation between gas transfer velocity and mean square slope, also based on field measurements, is then used to derive gas transfer velocities. Initial results demonstrate that the calculated transfer velocities exhibit magnitudes and a dynamic range which are generally consistent with existing field measurements. The new algorithm is used to construct monthly global maps of gas transfer velocity and to illustrate seasonal transfer velocity variations over a 1-year period. The measurement precision estimated from >106 duplicate observations of the sea surface by TOPEX and Jason-1 altimeters orbiting in tandem is better than 10%. The estimated overall uncertainty of the method is ±30%. The long-term global, area-weighted, Schmidt number corrected, mean gas transfer velocity is 13.7 ± 4.1 cm h−1. The new approach, based on surface roughness, represents a potential alternative to commonly used parameterizations based on wind speed.